MONO- AND POLYNUCLEAR COMPLEXES OF PT(II) WITH POLYPYRIDYL LIGANDS SYNTHESIS, SPECTROSCOPIC AND STRUCTURAL CHARACTERIZATION AND CYTOTOXIC ACTIVITY

An array of poly- and mononuclear complexes of Pt(II) with polypyridyl ligands is reported. The framework complexes[(PtCl2)2(bpp)2(l-PtCl2)](H2O)2 [bpp = 2,3-bis(2-pyridyl)pyrazine], [PtCl2(l-tptz)PtClNCPh]Cl [tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine],and mononuclear PtCl2(NH2dpt) [NH2dpt = 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole] have been prepared and structurally characterized.Both neutral and ionic complexes are present, with bifunctional and monofunctional Pt(II) moieties, whose size and shapeenable them to behave as novel scaffolds for DNA binding. Pt(II) complexes were tested for their biological activity. Cell viability assayand flow cytometric analysis demonstrated that these complexes, particularly [PtCl2(l-tptz)PtClNCPh]Cl, were effective death inducers inhuman colon rectal carcinoma HT29 cells and their cytotoxic activity was higher than that exerted by cisplatin. Morphological analysisof treated HT29 cells, performed by fluorescence microscopy after Hoechst 33258 staining, showed the appearance of the typical featuresof apoptosis. Moreover, our results suggested that mitochondria are involved in apoptosis induced by Pt(II) complexes in HT29 cells asdemonstrated by dissipation of mitochondrial transmembrane potential.